Gas compressor



V. J. SMITH GAS COMPRESSOR May 19, 1964 3 Sheets-Sheet 1 Filed Nov. 25, 1962 FIG.

OOOOOOOO OOO 000006000000 4%, JM W115 May 19, 1964 Filed Nov. 23, 1962 V. J. SMITH GAS COMPRESSOR 3 Sheets-Sheet 2 INVENTOR.

1 44i/V/74 E .2 5/7/76 rraiMf/ff y 19, 1964 v. J. SMITH 3,133,692

GAS COMPRESSOR Filed Nov. 23, 1962 3 Sheets-Sheet 3 INVENTOR.

VHAE/Vf/A/E .2 5/1/27? ArraPA/EYS United States Patent 3,133,692 GAS COMPRESSOR Valentine J. Smith, Loudonviile, N.Y., assignor to Mechanical Technology Incorporated, Latham, N.Y., a corporation of New York Filed Nov. 23, 1962, Ser. No. 239,556 10 Claims. (Cl. 230-162) This invention relates generally to gas compressors and more particularly to a unique gas compressor for delivery of small quantities of air or other gas at high pressure.

There are available today a variety of compressors operating upon a variety of principles. For delivery of relatively small quantities of gas at high pressure a reciprocating compressor is normally used. In applications where the capacity is very low a diaphragm compressor may be utilized. Both of these types of machines have mechanical limitations rendering them relatively undesirable for certain applications.

The invention herein disclosed has as its principal object the furnishing of a unique compressor to pump small volumes of gas and one in which very high gas discharge pressures can be achieved in a single stage.

It is another object of this invention to provide a gas compressor for delivery of small quantities of gas at high pressure wherein isolation of the gas being delivered from the remainder of the machine must be insured.

It is still a further object of this invention to provide a highly efficient compressor which is simple and reliable utilizing a process which approaches that of an isothermal process.

It is still a further object of this invention to provide a gas compressor in which the pressure ratio and volume flow are nearly independent of the nature of the process gas as the device approaches ideal isothermal conditions.

A gas compressor embodying the invention and the manner of using the same is described herein with references to the drawings in which:

FIG. 1 is a view of a compressor constructed in accordance with the teachings of this invention in which portions thereof are shown in section and portions are shown diagrammatically;

' FIG. 2 is a sectional view taken along the line 2-2 in the direction of the arrows as indicated in FIG. 1 illustrating the internal honeycomb structure of the compressor chamber with the flexible tubes therein in fully expanded condition;

FIG. 3 is a segmentary sectional view of one of the flexible tubes utilized in the compression chamber wherein the tube is shown in fully expanded condition;

FIG. 4 is a sectional view taken along the line 4-4 in the direction of the arrow as indicated in FIG. 3 showing the cross section of the expanded flexible tube;

FIG. 4a is a View of the cross section of the flexible tube shown in FIG. 3 wherein the tube is partially collapsed;

FIG. 5 is a View of an alternate form of compressor constructed in accordance with the teachings of this invention wherein a second compression chamber is utilized and in this view portions of the compressor are shown in section and portions are shown diagrammatically; and

FIG. 6 is a view of another embodiment of the compressor constructed in accordance with the teachings of this invention wherein the compression chamber is positioned concentrically Within the reservoir and in this view portions are shown in section and portions are shown diagrammatically.

In FIG. 1 a plurality of flexible containers or sacs 10 extend downwardly from line 11 into compression chamber 12. Each of the sacs is enclosed and supported within chamber 12 by a cylindrical perforated tube 13 within which it is suspended. Each tube is disposed within the chamber with its longitudinal axis parallel to the longitudinal axis of the chamber itself. The perforations of the tubes are indicated generally by the numeral 14 and as seen in FIG. 2 wherein a horizontal cross section is taken the plurality of tubes establish a honeycomb within the chamber 12.

Each of the sacs or containers 10 can be formed of any suitable material such as plastic or thin metal. In the preferred form the sacs are plastic and formed with upper end 15 through which opening or entrance 16 extends and lower end 17 with inner contoured sections 15a and 17a respectively projecting into the bag cavity 18. The contoured surfaces of 15a and 17a facing the sac inner wall 10a are provided so that the sac can readily be collapsed completely without pockets being formed at the upper or lower ends. For the same reason (complete bag collapse) the sac is irregular in horizontal cross section (see FIGS. 4 and 4a). One side 19 of the sac is formed with substantially parallel inner and outer walls Ida and 1% and side 29 is formed with inwardly protruding contoured portions 20a and Ztlb at the side extremities. In FIG. 4a the sac is shown in a slightly more collapsed condition than it is shown in FIG. 4 and by comparison of these figures the manner in which portions 20a and 2311b engage inner wall 111a of side 19 is seen. Each of the sacs 10 must be designed to operate within the pressure range to which they are subjected and to resist chemical interaction with the process gas within the sac and the fluid 21 within chamber 12. The sacs must also be designed to operate satisfactorily within the range of heating to which they will be subjected during compression of the process gas within the sacs as will be explained below.

The perforated tubes 13 can also be formed of any suitable material. Since the tubes are perforated pressure of fluid 21 upon the tubes within chamber 12 presents no problem and since the tubes are isolated from the process gas within the sacs problems of tube design in this regard are eliminated. The tubes however, must be able to resist chemical interaction with the fluid 21 and heating occurring during compression of the process gas.

Compression chamber 12 is connected to reservoir 22 by means of hydraulic line 23 extending from tank 12 and hydraulic line 24 extending from tank 12 through a hydraulic system including high pressure hydraulic pump 25, cooler 26 and a valve switching system which enables the pump 25 either to deliver fluid to the pressure tank 12 or to empty it back into a reservoir 22. The valve switch ing system will be described below in considering the operation of the device.

The purpose of the system is to receive the process gas at a low pressure at end 11a of line 11, operate upon the process gas and deliver the process gas at high pressure at end 11b of line 11. One way valve 27 is provided in end 11a of line 11. One way valve 27 is of the type normally used wherein it is desired to allow gas to flow in one direction only. Valve 27 is provided with a flap 27a which is designed to move only pivotally to the right as seen in FIG. 1 so that gas under low pressure impinging upon flap 27a on the left of the flap will cause the flap to pivotally open and allow the gas to enter sacs 10. The gas entering sacs 10 cannot return to end 11a of line 11 since flap 27a will not permit passage of the gas in that direction or to the left as seen in FIG. 1. Relief valve 2 8 is also provided. Relief valve 28 is a valve of the type having a movable plunger 29 which is spring pressed by means of spring 31) to the left as shown in FIG. 1. Valve 28 is designed to allow passage of gas to the right only when the gas is of sufficient pressure to disengage plunger 29 from valve seat 29a by overcoming the force with which spring Stl is maintaining the valve closed.

Both valves 27 and 28 as shown and described above are by way of example only. It is necessary only that valve 27 be a one way valve of the type which will allow gas under low pressure to pass therethrough and that valve 28 be a one way valve of the type which will allow gas of a higher pressure to pass therethrough so that gas entering through valve 27 will not be allowed to enter through valve 2% unless it is raised to a higher pressure level first.

In order to properly understand the system described above a typical cycle will now be considered. Assuming the process to start with the pressure tank 12 full of fluid 2i and the sacs 1t collapsed flat. The pump 25 evacuates tank 12 into the reservoir 22 through the cooler 26 allowing the sacs 1b to expand and draw in low pressure gas through valve 27. In FIG. 1 broken lines forming arrows are shown indicating a flow through the hydraulic system. Each of these broken lines is indicated by the letter A. The broken lines indicate the portion of the cycle described above. It is noted that the fluid travels through hydraulic line 23, valve 31, pump 25, valve 32, cooler 26 and hydraulic line 24 into reservoir 22.

When the sacs are full the flow direction of hydraulic fluid 21 is reversed and begins to fill the pressure tank 12. The gas inlet one way valve 27 closes and the gas pressure in the sacs It increases as fluid 21 enters the tank. At the required blow-off pressure the discharge valve 28 opens and the gas is delivered at constant pressure through end 11b of line 11the rate being dependent only on the delivery capacity of pump 25. During this portion of the cycle the fluid in the hydraulic lines follows the direction of the arrows shown in full lines. Each of these arrows is indicated by the letter B. Thus, the fluid leaves reservoir 22 by way of hydraulic line 24, passes through cooler 26, valve 33, pump 25, valve 34 and through hydraulic line 23 into chamber 12. When delivery is complete the valves 31, 32,- 33 and 34 again reverse direction and the cycle is reversed and repeats.

It is noted that cooler 26 is provided to cool the fluid 21 since the fluid 21 undergoes heating during compression of the process gas when the sacs are compressed and also by inefiiciency of the pump system. By proper design of the sacs, however, the ratio of surface area to volume can be large enough for high heat transfer out of the gas and the compression process can be made to approach the isothermal, in which case, the pressure ratio and volume flow are nearly independent of the nature of the process gas. It is further noted that the pressures inside and outside the sacs are at all times exactly equal, and consequently, the stresses in the sac material are the result of flexure only. Further, the only parts subject to high pressure differentials are the tank and the hydraulic pump. Volumetric efiiciency may be made very high by proper design of the sacs and the sac headers.

The embodiment set forth above is by way of example for a self-contained unit utilizing hydraulic fluid. This does not preclude, however, the use of the compression system when incorporated into another system from which a hydraulic head or a pressurized gas is available. Further, it is possible to use a solid, such as sand or steel balls. Also, a hydraulic pump is described. It is quite feasible to have the compression tank filled with gas or liquid or solid (e.g. rubber) and the compression achieved by the insertion of a ram or piston into the tank.

In the system shown in FIG, 1 the power delivery of pump is highly cyclic since evacuation of tank 21 requires very little power. Pump 25 also is required to deliver up to the full pressure head which may be a large range. It is obvious that a more efficient system would result if the power demand on the pump could be spread. In FIG. 5 a system is shown wherein the power demand upon the pump 35 can be spread more uniformly over F the whole cycle. Compression tanks 36 and 37 are provided each of half the total capacity of tank 12 in the embodiment of FIG. 1. Each of these tanks takes the whole pressure rise and the fluid from one tank is exhausted directly into the other. With such an arrangement the maximum pump power required of pump 35 is half that required of pump 25 in the embodiment of FIG. 1 and the capacity of the pump is halved. The maximum head remains unchanged and a more uniform power requirement is obtained. In effect the tank being charged during evacuation of the other tank acts as an accumulator capable of discharging into the other tank during the other half of the cycle. The system described in FIG. 5 is substantially identical to the system shown and described in FIG. 1 with the reservoir tank 22 of FIG. 1 being replaced by a compression tank 37, line 38 with inlet and outlet portions 38a and 38b respectively separated by valve 39 which is identical to valve 27 and valve 40 which is identical to valve 28 as shown in FIG. 1. Sacs 41 and cylindrical tubes 42 with perforations 43 formed therein are identical in construction and function with like parts within compression tank 12. Also, sacs 44 and perforated tubes 45 are provided within tank 36 and these members are identical in construction and function to like parts in tank 12. Line 46 connects with the sacs 44 within tank 36 and is provided with one way valves 47 and 43 between its inlet end 46a and outlet end 4612. Valves 4"! is identical to valve 27 in FIG. 1 and valve 48 is identical to valve 28 in FIG. 1.

In FIG. 5 the valves 49 and 50 in the hydraulic line between tanks 36 and- 37 are open and the tank 36 is being filled with fluid evacuated from tank 37. The fluid leaving tank 37 flows in the hydraulic lines in the direction of the arrows indicated by the letter C, out of tank 37 through cooler 51, valve 49, pump 35, valve 50 and into tank 36. As the fluid flows into tank 36 the sacs 44 are being collapsed and valve 48 is open with valve 47 closed so that gas from the sacs 44 is being delivered at high pressure through end 46b of line 46. At the same instant with respect to tank 37 valve 39 is open and valve 4% closed so that the sacs 41 in tank 37 are receiving gas at low pressure from end 38a of line 38.

On t e second half of the cycle valves 49 and 50 are closed and valves 52 and 53 are open so that the fluid 0 moves in the hydraulic lines in the direction of the arrows indicated by the letter D and tank 36 is being evacuated while tank 37 is being filled. In this half of the cycle valves 47 and 4b are open whereas valves 48 and 39 are closed so that gas under high pressure is being delivered at end 3812 of line 38 while gas under low pressure is being received in the sacs 44 within tank 36.

Other methods, of course, may be utilized to increase the efliciency of the system of FIG. 1.

As an example pumping 50 ft. /min. at STP of helium from 15 lbs/in. abs. to 600 lbs./in.

The adiabatic power required is 27.45 HR The isothermal power required is 12.07 HP. The pump maximum power required is 255.0 H.P.

Ideally, the time-average of the pump power is the isothermal power, 12.07 HP.

The pump power starts at zero during compression, rising to a maximum which remains constant during delivery.

Time Gas pressure Pump 11.1.

The pump power is the flow rate multiplied by the head rise. For single stage compression the head rise is fixed,

leaving the only variable to be the flow rate. above table it has been assumed that:

(a) The compression stroke is one-half of the total cycle time, i.e., the overall flow rate during compression is 100 ft. /min.

(b) The flow rate during compression is constant at 100 ft. min.

In order to reduce the maximum installed power required it is necessary to provide a high flow rate during the low-head part of the cycle, and a low flow nate at high ead.

Thus, if the capacity during evacuation is twice that during compression, both still at constant rate, the maximum installed power is reduced by 25%, the compression stroke now occupying of the cycle time.

However, even if the evacuation pumps were of infinite capacity so that compression occupies the whole of the cycle, the maximum installed power would be reduced by only 50% to 127.5 HR for the example quoted, or more than ten times the avenage power required.

The big power reduction therefore will come from falling flow rate during compression, in addition to extending compression over more than half the cycle.

The pump will have this characteristic naturally to some extent, but it may have to be exaggerated, or supplemented. Various methods of achieving this are possible.

One way is to utilize multiple compression pumps, which are cut out one-by-one as the head rises.

\Another method is to place mechanical devices on the pump to vary the capacity, such as variable diffuser area or inlet vanes.

A variable speed drive from the motor, e.g. similar to torque converter can be provided.

A head-multiplier flow-reducer device such as a hydraulic ram can also be provided. At a predetermined point during the compression stroke the pump flow is diverted to the low-pressure side of one or a number of hydraulic rams. The high-pressure piston of the ram can be in its own cylinder or can project directly into the compression tank.

By use of one or more of these methods, the maximum installed power required roan be reducedclosely to that of an equivalent reciprocator or turbo-machine.

In FIG. 6 an alternate embodiment of the invention is disclosed wherein the components of the device shown in FIG. 1 are arranged in a space saving manner. Essentially the device of FIG. 1 is an arrangement whereby the compression tank is placed within the reservoir and concentric therewith thereby reducing the length of hydraulic lines involved. The device shown in FIG. 6 operates exactly the way the device shown in FIG. 1 operates and a typical cycle will be described below. The components shown in FIG. 6 are given the same number as has been given like components in FIG. 1, however, the identifying numbers utilized in FIG. 6 are followed with a prime Thus, the sac, line, compression tank, cylindrical tube and perforations therein are indicated by the numerals 10", 11', 12, 13 and 14' respectively. The fluid, reservoir tank, hydnaulic line from the compression chamber, hydraulic line from the reservoir tank, pump, cooler, one way valve in end 11'a of line 11 and one way valve in end 11b of the line are indicated by the numerals 21', 22, 23, 24, 25, 26, 27 and 28 respectively. Also, the valves in the hydraulic line between the compression chamber and the reservoir are indicated by numenals 31, 32, 33' and 34'. In FIG. 6 the arrows illustrate the direction of flow of fluid 21 in the hydraulic system during evacuation of reservoir 22 and filling of compression chamber 12. The flexibility of the basic system allows for the space saving and equipment saving con-figuration of FIG. 6. It should also be noted that the flexibility of the system would likewise allow spreading of the system so that various components In the 6 could be placed at various locations. As an example the pump could be placed at a remote location.

Thus, among others, the several objects in the invention as specifically afonenoted, are achieved. Obviously, numerous changes in construction and rearrangement of parts might be resorted to without departing from the spirit of the invention as defined by the claims.

' I claim:

1. A compressor for raising the pressure level of a gas including in combination a collapsible container, a gas line to which said collapsible container is attached, a first end of said gas line, a second end of said gas line, a source of low pressure gas engaged with said first end, means for allowing low pressure gas in said gas line to enter said collapsible container, a compression chamber within which said container is disposed, a fluid supply, and means for injecting said fluid supply into said compression chamber under pressure whereby said gas is compressed, means for allowing the flow of gas from said collapsible container into said second end, said collapsible container being elongated and formed with its upper and lower ends having contoured portions projecting inwardly into said container cavity to receive in unbroken contact the facing portion of the container inner wall when the container is in collapsed condition.

2. A compressor for raising the pressure level of a gas including in combination a plurality of collapsible containers, a gas line, a point on said gas line to which said collapsible containers are attached, a first end of said gas line, a second end of said gas line, a source of low pressure gas engaged with said first end, a first one way valve between said first end and said point, a second one way valve between said second end and said point, said point being located between said first and second one way valves, said first one way valve being sensitive to low pressure and allowing gas from said first end to enter said collapsible containers, a compression chamber within which said containers are disposed, each of said containers being enclosed by a substantially rigid perforated tubular member, said tubular members being within said compression chamber and forming a honeycomb hori- Zontal cross section within said compression chamber, a first hydraulic line connecting with said compression chamber, a reservoir, a second hydraulic line connecting with said reservoir, a hydraulic pump between said first hydraulic line and said second hydraulic line, a cooler in circuit with said hydraulic pump, means for reversing the flow of fluid in said hydraulic lines and said cooler, said collapsible containens each including means formed on the internal surface thereof for receiving in unbroken contact the facing portion of the container inner wall when the container is in collapsed condition, whereby when said pump injects said fluid into said compression chamber through said first hydraulic line, said containers are collapsed and gas under high pressure is ejected from said containers through said second one way relief valve and whereby upon collapse of said containers, said fluid which has been heated due to compression action is passed through said cooler by said reversing means and returned to said reservoir.

3. A compressor for raising the pressure level of a gas including in combination a first collapsible container, a first gas line, a first point on said first gas line to which said first collapsible container is attached, a first end of said first gas line, a second end of said first gas line, a first source of low pressure gas engaged with said first end, a first one way valve between said first end and said first point, a second one way valve between said second end and said first point, said first one way valve being sensitive to low pressure and allowing gas from said first end to enter said first collapsible container, a first compression chamber within which said first container is disposed, a second collapsible container, a second gas line, a second point on said second gas line to which said second collapsible container is attached, a first end of said second gas line, a second end of said second gas line, a second source of low pressure gas engaged with said first end of said second gas line, a third one way valve between said first end of said second gas line and said second point, a fourth one way valve between said second end of said second gas line and said second point, said third one Way valve being sensitive to low pressure and allowing gas from said first end of said second gas line to enter said second collapsible container, a second compression chamber within which said second container is disposed, a first hydraulic line entering said first compression chamber, asecond hydraulic line entering said second compression chamber, a hydraulic pump between said first and second hydraulic lines, a cooler .in circuit with said hydraulic pump, means for reversing the flow of fluid in said hydraulic lines and said cooler, said collapsible containers each including means formed on the internal surface thereof for receiving in unbroken contact the facing portion of the container inner wall when the container is in collapsed condition, whereby when said pump injects said fluid into said first compression chamber through said first hydraulic line, said first container is collapsed and gas under high pressure is ejected from said first container through said second one way relief valve as low pressure gas enters said second container through said third relief valve and whereby upon collapse of said first container said reversing means will cause said fluid in said first chamber to pass through said cooler and into said second chamber through said second hydraulic line.

4. A compressor for raising the pressure level of a gas including in combination a collapsible container, a gas line to which said collapsible container is attached, a first end of said gas line, a second end of said gas line, a source of low pressure gas engaged with said first end, means for allowing low pressure gas in said gas line to enter said collapsible container, a compression chamber within which said container is disposed, a fluid supply, and means for injecting said fluid supply into said compression chamber under pressure whereby said gas is compressed, means for allowing the flow of gas from said collapsible container into said second end, said collapsible container being irregular in cross section with one side of the container formed with substantially parallel inner and outer walls and the remaining side formed with inwardly protruding contoured portions at the side eX- tremities whereby the inner faces of said container sides can collapse in substantially unbroken adjacency.

5. A compressor in accordance with claim 1 in which the collapsible container is irregular in cross section with one side of the container formed with substantially parallel inner and outer walls and the remaining side is formed with inwardly protruding contoured portions at the side extremities whereby the inner faces of the container sides can collapse in substantially unbroken adjacency.

6. A compressor in accordance with claim 5 in which the collapsible container is formed out of a flexible, nonmetallic material.

7. A compressor in accordance with claim 5 in which the collapsible container is formed out of thin metal.

8. A compressor in accordance with claim 3 in which a first plurality of like first collapsible containers are provided within said first compression chamber and attached to said first gas line between said first and second one way valves of said first gas line and a second plurality of like second collapsible containers are provided within said second compression chamber and attached to said second gas line between said first and second one way valves of said second gas line.

9. A compressor in accordance with claim 8 in which each of the collapsible containers in each of the compression chambers is surrounded by a like substantially rigid perforated member supporting said containers and establishing a honeycomb horizontal cross section within the chamber.

10. A compressor in accordance with claim 2 in which the compression chamber is cylindrical and the reservoir is cylindrical and the compression chamber is positioned concentrically within the reservoir.

References Cited in the file of this patent UNITED STATES PATENTS 225,930 Hoster Mar. 30, 1880 1,377,654 Baumgardner May 10, 1921 1,563,166 Corblin Nov. 24, 1925 2,971,465 Caillaud Feb. 14, 1961 FOREIGN PATENTS 756,149 Great Britain Mar. 15, 1954 

1. A COMPRESSOR FOR RAISING THE PRESSURE LEVEL OF A GAS INCLUDING IN COMBINATION A COLLAPSIBLE CONTAINER, A GAS LINE TO WHICH SAID COLLAPSIBLE CONTAINER IS ATTACHED, A FIRST END OF SAID GAS LINE, A SECOND END OF SAID GAS LINE, A SOURCE OF LOW PRESSURE GAS ENGAGED WITH SAID FIRST END, MEANS FOR ALLOWING LOW PRESSURE GAS IN SAID GAS LINE TO ENTER SAID COLLAPSIBLE CONTAINER, A COMPRESSION CHAMBER WITHIN WHICH SAID CONTAINER IS DISPOSED, A FLUID SUPPLY, AND MEANS FOR INJECTING SAID FLUID SUPPLY INTO SAID COMPRESSION CHAMBER UNDER PRESSURE WHEREBY SAID GAS IS COMPRESSED, MEANS FOR ALLOWING THE FLOW OF GAS FROM SAID COLLAPSIBLE CONTAINER INTO SAID SECOND END, SAID COLLAPSIBLE CONTAINER BEING ELONGATED AND FORMED WITH ITS UPPER AND LOWER ENDS HAVING CONTOURED PORTIONS PROJECTING INWARDLY INTO SAID CONTAINER CAVITY TO RECEIVE IN UNBROKEN CONTACT THE FACING PORTION OF THE CONTAINER INNER WALL WHEN THE CONTAINER IS IN COLLAPSED CONDITION. 